Effects of aristolochic acid I and/or hypokalemia on tubular damage in C57BL/6 rat with aristolochic acid nephropathy

BACKGROUND/AIMS: This study was designed to investigate the roles of aristolochic acid I (AA-I) and hypokalemia in acute aristolochic acid nephropathy (AAN). METHODS: After an adaptation period (1 week), a total of 40 C57BL/6 mice (male, 8 weeks old) were divided into four groups: I (control group), II (low potassium [K] diet), III (normal K diet with administration of AA-I [10 mg/kg weight]), and IV (low K diet with AA-I). After collecting 24 hours of urine at 2 weeks, the mice were sacrificed, and their blood and kidneys were obtained to perform immunochemical staining and/or Western blot analysis. RESULTS: Proteinuria, glycosuria, and increased fractional excretion of sodium and K were prominent in groups III and IV (p < 0.05). Diffuse swelling and poor staining of collecting duct epithelial cells were evident in the medullas of group II. Typical lesions of toxic acute tubular injury were prominent in the cortices of groups III and IV. Α-Smooth muscle actin (α-SMA) was higher in the cortices of the mice in groups III and IV versus group II (p < 0.05), and higher in the medullas of group IV than groups I and III (p < 0.05). E-cadherin was higher in the cortices of groups III and IV compared to group I (p < 0.05). The F4/80 value was higher in the cortices and medullas of groups II, III, and IV compared to group I (p < 0.05), particularly in the case of group II. CONCLUSIONS: AA-I can induce acquired Fanconi syndrome in the acute stage of AAN. Macrophages appear to play a key role in the pathogenesis of AAN and hypokalemic nephropathy. It remains uncertain whether hypokalemia plays any role in AAN and hypokalemia.

Notch signaling in the collecting duct regulates renal tubulointerstitial fibrosis induced by unilateral ureteral obstruction in mice

BACKGROUND/AIMS: Mind bomb-1 (Mib1) encodes an E3 ubiquitin ligase, which is required for the initiation of Notch signaling. Recently, it was demonstrated that the renal collecting duct plays an important role in renal fibrosis. Here, we investigated the role of Notch signaling in renal fibrosis using conditional knockout mice with the specific ablation of Mib1 in renal collecting duct principal cells. METHODS: Mib1-floxed mice (Mib1f/f ) were crossed with aquaporin 2 (AQP2)-Cre mice in order to generate principal cell-specific Mib1 knockout mice (Mib1f/f :AQP2-Cre+). Unilateral ureteral obstruction (UUO) was performed, and mice were sacrificed 7 days after UUO. RESULTS: After performing the UUO, renal tubulointerstitial fibrosis and the expression of transforming growth factor β were markedly enhanced in the obstructed kidneys of Mib1f/f mice compared with the sham-operated kidney of Mib1f/f mice. These changes were shown to be even more pronounced in the obstructed kidneys of Mib1f/f :AQP2-Cre+ mice than in those of the Mib1f/f mice . Furthermore, the number of TUNNEL-positive cells in renal collecting duct was higher in the obstructed kidneys of Mib1f/f :AQP2-Cre+ mice than in the kidneys of Mib1f/f mice. CONCLUSIONS: Notch signaling in the renal collecting duct plays an important role in the regulation of renal tubulointerstitial fibrosis and apoptosis after UUO.

The Expression of Label-retaining Cells (LRCs) in Developing Rat Kidney / 대한해부학회지

Adult stem cells often have a low cycling rate and contribute to repair after injury by self-renewal and multiple cell division. In this study, we investigated the changes of the expression of label-retaining cells (LRCs) in developing rat kidneys which administered 5-bromo-2'-deoxy-uridine (BrdU) at embryonic day 18. In the cortex, BrdU-positive cells are localized mainly at embryonic day 18 and 20, but BrdU-positive cells after birth were rapidly decreased and almost not observed at day 14 after birth. In the medulla, the numerous BrdU-positive cells were markedly decreased in outer medulla at day 1 after birth and initial part of inner medulla at day 4 and 14 after birth, while the expression of BrdU-positive cells in the middle part (IMm) and terminal part of inner medulla (IMt) were not changes. At day 31 after birth as well as adult, BrdU-positive cells were remained in the IMm and IMt, which were mainly localized inner medullary collecting duct except a few BrdU-positive cells in the interstitium. Taken together, these observations suggest that the expression of LRCs were moved from cortex to medulla in developing kidney and the most LRCs are localized among renal epithelial tubular cells of the renal papilla in adult rat kidney.

Expression of Aquaporin-6 in Intercalated Cell subtypes in Rat and Mouse Kidney / 대한해부학회지

Aquaporin-6 (AQP6) is a water channel protein located in intracellular vesicles of the proximal tubules and in intercalated cells (ICs) in the collecting duct (CD) of the rat kidney. The function of AQP6 is unknown. However, it colocalizes with vacuolar H+-ATPase in type-A ICs, indicating that it may be important for the function of proton pumps in these cells. The aims of this study were to compare the expression of AQP6 between rat and mouse kidneys, and to establish which types of IC express AQP6. Kidneys of adult male rats and mice were processed for immunohistochemistry using antibodies against AQP6, H+-ATPase, and anion exchanger 1 (AE1). AQP6 was expressed in the S1, S2, and S3 segments of the proximal tubule and in ICs of the CD and connecting tubule (CNT) in both rats and mice. In the rat proximal tubule, AQP6 immunoreactivity was present in intracellular vesicles, whereas in the mouse proximal tubule it was present in the brush border as well as in intracellular vesicles. Triple immunostaining for AQP6, AE1, and H+-ATPase revealed that AQP6 was expressed only in type-A ICs in the CDs and CNTs of both rats and mice, and that the staining was diffuse throughout. There was no AQP6 labeling of type-B ICs, non-A-non-B ICs, or principal cells. The functional significance of the expression of AQP6 in proximal tubule cells and type-A ICs remains to be established. We propose that AQP6 is involved in the retrieval and maintenance of H+-ATPasecontaining vesicles in acid-secreting epithelial cells in the kidney.

Expression of Aquaporin-3 and Aquaporin-4 in Aquaporin-1 Knockout Mice / 대한해부학회지

Recent studies demonstrated impaired urinary concentrating ability in AQP1 knockout mice. To establish of the lack of AQP1 was associated with compensatory changes in other aquaporins, we examined the expression of AQP3 and AQP4 in AQP1 knockout mice. In AQP1 (+/+) mice, there was strong basolateral AQP3 immunostaining in principal cells throughout the collecting duct and strong basolateral AQP4 immunostaining in IMCD cells and principal cells in the medulla. In AQP1 (-/-) mice, there was an increase in AQP3 immunostaining in principal cells in cortex and outer medulla, but no changes in cellular distribution of labeling. In contrast, AQP4 immunostaining was slightly decreased and there was a surprising decrease in cell height and disappearance of immunolabeling of the lateral cell membrane in IMCD cells with only basal labeling remaining. Immunnoblot analysis confirmed the increase in AQP3 expression in cortex (259+/-50%, P<.0.01), outer medulla (607+/-115%, P<0.01) and inner medulla (1,289+/-174%, P<0.0001), and the decrease in AQP4 expression in the inner medulla (31+/-2%, P<0.02) of AQP1 (-/-) compared with AQP1 (+/+) mice (values in AQP1 (-/-) expressed as percentage of AQP1 (+/+)). In summary, AQP1 gene deletion is associated with an upregulation of AQP3 and a downregulation of AQP4. Taken together, these observations suggest that AQP3 and AQP4 are differently regulated and the basolateral water channel expression is upregulated in the cortical and outer medullary collecting duct in AQP1 knockout mice. The significance of the disappererance of AQP4 immunoreactivity in the lateral plasma membrane of IMCD cells in AQP1 knockout mice remains to be established.

Selective Proximal Tubule Injury and Progressive Renal Failure due to Ifosfamide and Cisplatin in a Patient with Ovarian Cancer / 대한신장학회지

Ifosfamide-induced nephrotoxicity is usually manifested in the form of Fanconi syndrome and the combination of cisplatin enhances ifosfamide-induced nephrotoxicity. We here report a case of report specific proximal tubular dysfunction and progressive renal failure after ifosfamide and cisplatin chemotherapy in a 32-year old woman with ovarian cancer. The patient was referred to our department due to severe hypokalemia and elevated serum creatinine. Her renal function was abruptly impaired and serum and urine electrolytes were consistent with Fanconi syndrome. The kidney biopsy revealed atrophy and falling of renal tubular cells, and immunohistochemical staining with aquaporin 1 (AQP1) revealed that injured epithelial cells were proximal tubular cells. This finding suggests that ifosfamide selectively impairs proximal tubule function and combination with cisplatin causes progressive renal failure

A case of Gitelman's Syndrome with Chronic Hypotension and Normomagnesemia / 대한신장학회지

Gitelman's syndrome is a heritable renal disorder characterized by hypomagnesemia, hypokalemia and hypocalciuria. Interestingly, we have experienced one patient who had chronic hypotension, normal serum magnesium level, normal plasma ionized magnesium level, hypokalemia and hypocalciuria. Immunohistochemistry showed the absence of NCCT staining in renal tissues of the patient. We report the case of atypical Gitelman's syndrome with a brief review of related literature.

Immunocytochemical Study of Calbindin D(28k) Positive Cells in the Developing Rat Kidney / 대한해부학회지

Calbindin D(28k),a calcium binding protein,is found in various tissues,including some cells in the distal nephron.It plays an important role in the regulation of calcium reabsorption. We previously reported the expression of calbindin D(28k) in adult rat kidney.However,the exact time of expression during differentiation in the embryonic kidney is not known.During development,intercalated cells are deleted from the medullary collecting duct by two distinct mechanisms.However,the reason for the different modes of cell death is not known.As calbindin is reported to protect cells against apoptosis,we examined the expression of calbindin D(28k) in the developing rat kidney.Kidneys from 16-,17-,18-and 20-day-old fetuses and 1-,3-,5-,7-,14-and 21-day-old pups and adult Sprague awley rats were processed for immunohistochemistry using a monoclonal antibody against calbindin D(28k) .Intercalated cells were identified by immunostaining for H+ -ATPase and by electron microscopy.Calbindin D(28k) immunoreactivity first appeared in subpopulations of cells in the connecting tubule and medullary collecting duct in the 17-day-old fetus.In the connecting tubule,calbindin D(28k) was expressed only in H+ -ATPase negative connecting tubule cells,and there was no labeling of intercalated cells.In the medullary collecting duct,calbindin D(28k) immunostaining was observed in a few cells with apical H+ -ATPase,characteristic of type A intercalated cells.The numbers of calbindin D(28k) -positive type A intercalated cells increased from day 18 of gestation.In contrast,there was little or no calbindin D(28k) immunoreactivity in the type B intercalated cells or principal cells.During the first two weeks after birth,calbindin D(28k) -positive type A intercalated cells were lost from the terminal part of the medullary collecting duct by simple extrusion. After two weeks,calbindin D(28k) immunostaining decreased in the type A intercalated cells throughout the medullary collecting duct.However,the immunoreactivity of calbindin D(28k) in the cortical collecting duct was increased in some of the type A intercalated cells and the adult pattern was observed in 21-day-old pups.Thus,we propose that the different expression of calbindin D(28k) in type A and type B intercalated cells may be responsible-at least partly-for the different modes of cell death demonstrated in these cells during kidney development.

Immunolocalization of Protein Kinase C Isoenzymes alpha, betaI, betaII and gamma in Adult and Developing Rat Kidney

Protein kinase C (PKC) plays an important role not only in signal transduction mechanisms in various biological processes, but also in the regulation of growth and differentiation during development. We studied the classical PKC alpha, betaI, betaII and gamma, with regard to their expression in adult and developing rat kidney. PKCalpha appeared in the ureteric bud at embryonic day (E) 16, and the proximal and distal anlage at E18. After birth, the immunoreactivity of PKCalpha gradually decreased. In adult, PKCalpha was expressed intensely in the connecting tubule (CNT), the collecting ducts (CD) and the renal corpuscle, and weakly in the proximal and distal tubules. PKCbetaI appeared in the ureteric bud at E16, and the proximal anlage at E18. After birth, the immunoreactivity of PKCbetaI gradually disappeared from the CD and proximal tubule. In adult, PKCbetaI was expressed in the intercalated cells of the CNT and cortical CD, the proximal straight tubule, and the renal corpuscle. PKCbII appeared in distal anlage at E18, and increased markedly after birth. In the CD, PKCbetaII immunoreactivity appeared after birth. In adult, PKCbetaII was expressed in the distal tubule, the CNT and the CD. The immunoreactivity for PKCgamma appeared only in the proximal anlage at E18, and increased temporally around the time of birth. However, no immunoreactivity for PKCgamma was observed in adult rat kidney. These results indicate that classical PKC isoforms appear to play a role in the regulation of various renal functions and differentiation within specific functional units of the uriniferous tubule in rat kidney.

Identification of a novel murine organic anion transporter like protein 1 (OATLP1) expressed in the kidney

The organic anion transporters (OATs) are expressed in various tissues, primarily in the kidney and liver, but they are also expressed in the placenta, small intestine, and the choroid plexus, which are all epithelial tissues that transport xenobiotics. Six isoforms of OATs are currently known. Considering the variety of organic anionic compounds, other OATs isoforms can be assumed. In this connection, we have searched for a new isoform in the expressed sequence tag (EST) database. We found the new candidate clone AK052752 in the mouse kidney cDNA library and we named it mouse organic anion transporter like protein 1 (mOATLP1). The mOATLP1 cDNA consisted of 2221 base pairs that encoded a 552 amino acid residue protein with 12 putative transmembrane domains. The deduced amino acid sequence of mOATLP1 showed 37 to 63% identity to other members of the OAT family. According to the tissue distribution based on Northern blot analysis, 2.7 kb and 2.9 kb mOATLP1 transcripts (approximate sizes) were observed in the kidney and liver. An 85-kDa band (approximate) was detected using Western blot analysis of mouse kidney performed with a synthesized oligopeptide-induced mOATLP1 antibody. Immunohistochemical results showed mOATLP1 was stained in the blood vessels, glomeruli (the parietal epithelial cells and podocytes), distal convoluted tubules, connecting tubules, and inner medullary collecting tubules. mOATLP1 appears to be a novel candidate for an organic anion transporter isoform identified in the kidney.

Ultrastructural Localization of the Ammonium Transporter Protein, RhBG, in the Intercalated Cell of Rat Kidney Collecting Duct / 대한해부학회지

Ammonia excretion in the renal collecting duct is critical in the regulation of the acid-base homeostasis. A novel family of ammonium transporter protein, Rh B Glycoprotein (RhBG) was recently identified in the mouse and rat kidney collecting duct. The purpose of this was to examine the ultrastructural localization of RhBG in the collecting duct. Rat kidneys were processed for light and electron microscope immunocytochemistry using anti-RhBG rabbit polyclonal antibody. Strong RhBG immunolabeling was observed in the basolateral plasma membrane of type A intercalated cells in the collecting duct. In contrast, RhBG labeling was very weak or negative in type B intercalated cells and principal cells. Transmission electron microscopy confirmed that RhBG immunostaining was located mainly in the basolateral plasma membrane and infoldings of type A intercalated cells, but very weak in type B cells. RhBG labeling was not observed in the apical plasma membrane both in type A and B cells. These results demonstrate that RhBG is a basolateral transporter in acid-secreting type A cells and may mediate ammonia excretion in the collecting duct.

Expression of an Anion Exchanger Pendrin in Human Kidney / 대한해부학회지

It has been reported that new apical anion exchanger perndrin, encoded by the pendred syndrome (PDS/pds, Slc26A4) gene, was expressed in the AE1-negative intercalated cells of rat and mouse kidneys. The purpose of this study was performed that expression of pendrin in the subtypes of intercalated cells in human kidney. The normal human renal tissues obtained from nephrotomized kidneys for renal cell carcinoma were fixed in periodate-lysine-paraformalde-hyde, and processed for immunohistochemistry. Subtypes of intercalated cells were identified by using antibodies for H(+)-ATPase and AE1, and connecting tubule cells and principal cells of collecting duct were identified using antibodies for calbindin D28K and AQP2, respectively. In human kidney, pendrin was expressed in the apical domain of AE1-negative intercalated cells including type B cells with diffuse and/or basolateal H(+)-ATPase, non A-non B (non -A/B) type intercalated cells with apical H(+)-ATPase and bipolar type of intercalated cells with apical and basolateral H(+)-ATPase. The AQP2-positive principal cells of cortical collecting duct were also had apical pendrin immunoreactivity. However, there was no pendrin immunoreactivity in AE1-positive type A intercalated cells, calbindin D28K-positive connecting tubule cells, and AQP2-positive medullary collecting duct. These results suggest that pendrin is an apical anion exchanger not only in the AE1-negative intercalated cells (type B, non-A/B and bipolar cells) but also in the principal cells of cortical collecting duct, and has an essential role in HCO3-secretion in human kidney.

Expression of Osteopontin in Chronic Potassium Depletion-induced Renal Injury / 대한해부학회지

Osteopontin (OPN), a potent chemoattractant for the monocyte/macrophage infiltration, is highly upregulated in the renal tubular epithelium during various pathologic conditions associated with tubulointerstitial injury. The purpose of this study was to establish the distribution and localization of OPN in the tubulointerstitial injury induced by chronic potassium (K+) deprivation in the rat kidney. Sprague-Dawley rats were fed either a normal or a K+ -deficient diet for 2 weeks. Kidney tissues were preserved by in vivo perfusion with paraformaldehyde-lysine-periodate (PLP) and processed for light and electron microscope immunocytochemistry using monoclonal antibodies to OPN. K+ -depleted kidneys showed tubulointerstitial injury with renal hypertrophy, monocyte/macrophage infiltration, interstitial fibrosis, and OPN overexpression. OPN immunoreactivity was observed only in the descending thin limb (DTL) and the papillary surface epithelium (PSE) in the control kidney. However, the OPN labeling was observed not only in DTL and PSE but also in the thick ascending limb (TAL) in the K+ -depleted kidney. Electron microscopy revealed that OPN induced in the TAL cells was not located in the basal plasma membrane, but in the Golgi apparatus and in subapical cytoplasmic vesicles. There was no OPN expression in the epithelium of the collecting ducts, which showed marked morphological damages with mononuclear cell infiltration. These results demonstrate that chronic K+ -deprivation causes renal injury with the increased OPN expression in tubular epithelial cells. However, the localization of the induced OPN suggests other roles rather than a chemoattractant function in this renal injury model.

Effect of Pretreatment of Mycophenolate Mofetil on Apoptotic Cell Death and Map Kinases Activation in Rat Kidneys with Ischemia/Reperfusion Injury / 대한신장학회잡지

BACKGROUND: This study was performed to investigate the effects of pretreatment of mycophenolate mofetil (MMF) on mitogen activated protein (MAP) kinase expression and apoptotic cell death in rat kidneys with ischemia/reperfusion (I/R) injury. METHODS: Three experiments were done separate ly, In the first experiment, the effect of MMF (20 or 60 mg/kg) on I/R injury was observed. In the second experiment, MAP kinase expression were observed according to the time interval after I/R injury. Finally, the effect of pretreatment of MMF (20 or 60 mg/kg) on I/R injury in terms of apoptotic cell death and MAP kinases were evaluated. We also studied pro-inflammatory cytokines (IL-1 and TNF-alpha) using PCR. RESULTS: BUN and Serum creatinine level in creased in rats with I/R injury but their levels were significantly decreased with MMF Pro-inflammatory cytokines (TNF-alpha & IL-1) and apoptosis-related gene (caspase-1 and caspase-3 activities) were also significantly decreased as compared with rats with I/R injury. Expressions of MAP kinase were significantly increased in kidneys with I/R injury compared with sham-operated control, but significantly decreased with MMF pretreatment. CONCLUSION: Pretreatment of MMF showed a significant decreases of apoptotic cell death, apoptosis-related genes, and MAP kinase expression. This may explain beneficial effect of MMF on subsequent I/R injury.

The Effect of Oxytocin on Subcellular Localization of Aquaporin-2 in Rat Kidney: an Ultrastructural Immunocytochemical Study / 대한신장학회잡지

BACKGROUND: The aquaporin-2 (AQP2) water channel is mainly located in the apical plasma membrane of epithelial cells in the connecting tubule and collecting ducts, but there has been some evidence of a moderate amount of basolateral localization of AQP2 in these nephron segments. Previous in vitro microperfusion studies showed that oxytocin has an antidiuretic action most likely mediated by the vasopressin V2 receptor (V2R) in rat inner medullary collecting duct. METHODS: By using ultrastructural preembedding immunocytochemistry with 1 nm immunogold in male Sprague-Dawley rat kidneys, we investigated the acute (60 min) effect of oxytocin (10 U) on the subcellular localization of AQP2 and tested whether the effect of oxytocin is prevented by a V2R antagonist, OPC-31260 (OPC). RESULTS: In control rat kidneys, AQP2 was mainly expressed in the apical plasma membrane and subapical vesicles in the connecting tubule (CNT) cells, principal cells of cortical (CCD), outer medullary collecting duct (OMCD) and initial part of inner medullary collecting duct (IMCD), and IMCD cells of terminal part of IMCD. Basolateral AQP2 labeling was observed in the CNT cells and IMCD cells. In contrast, there was little basolateral AQP2 labeling in the CCD and OMCD principal cells. Oxytocin treatment induced apical immunolabeling of AQP2 and caused an increase of AQP2 immunolabeling in the basal part including basolateral plasma membrane in the CNT cells, principal cells of CCD, OMCD and initial part of IMCD, and IMCD cells of terminal part of IMCD. Pretreatment of rats with a V2R antagonist OPC before oxytocin treatment caused translocation of AQP2 from the apical plasma membrane to the subapical vesicles. However, AQP2 labeling of basolateral plasma membrane was unchanged or slightly increased. CONCLUSION: Oxytocin induces an increase of AQP2 expression not only in the apical plasma membrane but also in the basolateral plasma membrane. Pretreatment with a V2R antagonist blocked redistribution of apical AQP2 immunolabeling, but did not cause retrieval of AQP2 from the basolateral plasma membrane. These results suggest that apical and basal targeting of AQP2 are regulated by different mechanisms.

Expression of H(+)-ATPase in Inner Medullary Collecting Duct Cells of Aquaporin-3-Deficient Mice / 대한해부학회지

It has been reported that the decrease in urinary pH observed in AQP1 null mice with a urinary concentrating defect is due to upregulation of H(+)-ATPase in the IMCD. This is thought to be caused by the chronically low interstitial osmolality in these animals. To explore whether increase of H(+)-ATPase expression in the IMCD is associated with changes in the prolonged decrease of interstitial osmolality, we examined the expression of H(+)-ATPase and Na(+)-H(+) exchanger (NHE3) using light and electron microscopic immunocytochemistry in the kidneys of AQP3 null mice which are polyuric and manifest a urinary concentrating defect because of an inability to create a hypertonic medullary interstitium. In both AQP3 (-/-) and AQP1 (-/-) mouse kidneys, type A intercalated cells in cortical and medullary collecting ducts are slightly activated, and strong H(+)-ATPase immunostaining was present in the apical plasma membrane of IMCD cells, whereas no H(+)-ATPase labeling was observed in IMCD cells in wild type mice. No differences of the immunoreactivity for NHE3 in the proximal tubule and thick ascending limb of loop of Henle were observed between AQP3 or AQP1 (-/-) mice and AQP3 (+/+) mouse. These results suggest that the induction of H(+)-ATPase expression in IMCD cells of AQP3 null mice, as well as AQP1 null mice, may be related to their chronically low interstitial osmolality.

H+ -ATPase Pump Defects of Distal Renal Tubular Acidosis as Initial Manifestation of Systemic Lupus Erythematosus / 대한신장학회잡지

Systemic lupus erythematosus (SLE) is a multisystem disease with marked variability in its manifestation. Tubulointerstitial involvement is well recognized in SLE. But usually the tubular dysfunction is latent and usually presents after diagnosis of SLE. We report a 20 years old female whose initial symptom of SLE was distal renal tubular acidosis (RTA). She presented with severe muscle weakness at emergency room with laboratory fingding consistent with distal RTA. After several months she developed fever, arthritis, serologic fingding which was compatible to diagnose SLE. We report a case whose initial symptom of SLE had been distal RTA.

Expression of alphasmooth Muscle Actin, Aquaporin 1 and Renin after Blocking AT1 Receptor in Developing Renal Arterial System of Rat / 대한신장학회잡지

BACKGROUND: Recent studies have demonstrated that renin, alphasmooth muscle actin(ASMA) and aquaporin-1(AQP1) participate in the development of renal arterial system. The components of the renin- angiotensin system have been shown to function as growth factors, apart from their classical roles in controlling blood volume and homeostasis. Interestingly, the vasoconstrictor angiotensin II(ANG II) appears to participate in the regulation of angiogenesis in various tissues. The present study examined the effect of ANG II type-1(AT1) receptor blocker losartan given during pregnancy or newborn rats on the expression of renin, ASMA and AQP1 in the developing renal arterial system. METHODS: Pregnant and newborn rats received losartan(10 mg/kg/day) or saline for 4 and 8 days from E14 to parturition, and for 4 and 9 days starting at day 1 after birth, respectively. Kidneys of 17-day-old fetuses and 1-, 4-, and 9-day- old pups were processed for immunohistochemistry using antibodies to renin(1 : 10,000), ASMA(1 : 1,000), and AQP1(1 : 1,000). RESULTS: In all pregnant groups, there were no differences in immunostaining for renin, ASMA, and AQP1 between losartan treated groups and saline treated groups. In all newborn groups, however, blockade of AT1 receptor with losartan found to increase expression of renin and ASMA but to have no effect on expression of AQP1 in the developing renal arterial system. CONCLUSION: These results suggest that AQP1 expression is not associated with renin or ASMA expression during development of renal arterial system.

Developmental Expression of eNOS in the Rat Renal Vasculature / 대한해부학회지

Nitric oxide (NO) has an important role in maintaining basal renal blood flow (RBF) and glomerular filtration rate (GFR) in the developing kidney. However, renal endothelial NO synthase (eNOS) has not been localized in the developing kidney. The purpose of this study was to examine the expression and localization of eNOS in the developing rat kidney using immunohistochemistry and western blotting. Kidneys from 14 (E14)-, 16 (E16)-, 18 (E18)- and 20-day-old (E20) fetuses, 1 (P1)-, 4 (P4)-, 7 (P7)-, 14 (P14)- and 21-day-old (P21) pups, and adult rats were extracted for immunohistochemistry, and western blot analysis. In the adult rat kidney, eNOS was expressed strongly in the endothelial cells of the arcuate artery and the vascular bundle in the medulla. Endothelial cells of the glomerulus and peritubular capillary network were weakly labeled for eNOS. There was no eNOS immunoreactivity in the uriniferous tubules, including the proximal tubules. In the developing rat kidney, eNOS appeared in the endothelial cells of the capillary network from E14. In the developing glomerular capillary, immunoreactivity for eNOS was observed in the S-shaped bodies (stage II glomeruli) and stage III glomeruli, whereas mature glomeruli (stage IV glomeruli) were faintly immunolabeled for eNOS. These eNOS-positive early-stage developing glomeruli were observed in the nephrogenic zone until seven days after birth. In the endothelial cells of the peritubular capillary network, eNOS was strongly expressed in the fetus and gradually decreased in intensity after birth. The endothelial cells of the arcuate artery were strongly immunoreactive for eNOS from E16 to the adult stages. In the renal medulla, eNOS was expressed in the endothelial cells of the capillary network surrounding the developing medullary collecting ducts of the fetal kidney. After birth, eNOS immunoreactivity gradually disappeared from the vasculature of the renal medulla and only remained in the vasa recta. In conclusion, the strong expression of eNOS in the early stages of the developing vasculature suggests that eNOS may contribute to angiogenesis and/or critically participate in the hemodynamics of the immature kidney.

Effect of Furosemide on the Morphogenesis of Neonatal Rat Renal Papilla / 대한해부학회지

In developing rat kidney, apoptosis plays an important role in the morphogenesis of renal papilla, and hyperosmolality is well known to be one of regulating factor in apoptosis. The aim of this study was to determine the effect of hypoosmolality induced furosemide in neonate on cell proliferation and apoptosis in renal papilla. One-dayold pups were given two times a day, at 12 hour intervals, subcutaneous injection of furosemide (10 mg/kg BW) or saline for 4 days or 7days. We identified thick ascending limb by labeling with antibody to BSC1 (bumetanide-sensitive Na/K/2Cl cotransporter) and type A intercalated cell in collecting duct by labeling with antibody to band 3 protein. We also inspected apoptosis with TdT-mediated dUTP nick end labeling (TUNEL) method and cell proliferation with immunostaining for proliferating cell nuclear antigen (PCNA). The effect of hypoosmolality induced furosemide on neonatal rat kidney. 1) In furosemide-treated animals, body and kidney weights were reduced compare to control groups. the length of renal papillae of furosemide-treated groups were shortened compare to control groups. 2) Transformation from a cuboidal epithelium of thick ascending limb to a squamous epithelium of ascending thin limb in renal papilla was delayed in furosemide-treated groups. 3) In the inner medullary collecting duct of furosemide-treated groups, elimination of type A intercalated cells was delayed compared to control groups. 4) Furosemide treatment reduced the apoptotic index in transforming thick ascending limb of Henle's loop and collecting duct in renal medulla. 5) PCNA-positive cells in the transforming thick ascending limb of Henle's loop and the collecting duct in renal medulla were decreased in number in furosemide-treated groups compared to control groups. These finding suggest that renal hypoosmolality induced furosemide treatment decrease not only apoptosis but also cell proliferation and may retard renal papilla growth at least in neonatal rat kidney.